Light projecting apparatus, distance measuring apparatus, and light projection control method of laser light

This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2021-182794, filed on Nov. 9, 2021, the entire contents of which are incorporated herein by reference.

An embodiment of the present invention relates to a light projecting apparatus, a distance measuring apparatus, and a light projection control method of laser light.

The automatic driving technique requires a technique for detecting an object present around a vehicle in a non-contact manner at high speed and with high accuracy. A time of flight (ToF) method is generally adopted in which a distance to an object is detected based on a time until laser light emitted from a vehicle is reflected by the object and received. In order to detect an object around a vehicle, it is necessary to irradiate a relatively wide range with laser light, and a scanning mechanism for periodically scanning the laser light in a two-dimensional direction is often provided. However, it is not easy to downsize the scanning mechanism.

In addition, since the laser light has extremely high light intensity per unit area as compared with other illumination light, there is a risk of damaging human eyes when the laser light directly enters the human eyes. Therefore, it is necessary to set the light intensity conforming to the laser safety standard. However, when the light intensity is weakened, the laser light does not reach a distant object, and the range in which the distance can be measured is limited. Further, a laser light source has a limited light emission capability, and it is necessary to use a plurality of laser light sources for an application that further extends a range in which a long distance can be measured. However, in the case of using a plurality of laser light sources, an optical system or the like that combines the plurality of laser light sources into one laser beam becomes complicated, which leads to an increase in design cost and an increase in size of a light projecting system.

a plurality of light projectors, each being capable of switching an emission direction and an emission timing of an optical signal; and a plurality of first controllers, each controlling an emission direction and an emission timing of an optical signal emitted from a corresponding light projector among the plurality of light projectors. According to one embodiment, a light projecting apparatus has:

Hereinafter, embodiments of a light projecting apparatus, a distance measuring apparatus, and a light projection control method of laser light will be described with reference to the drawings. Hereinafter, the main components of the light projecting apparatus and the distance measuring apparatus will be mainly described, but the light projecting apparatus and the distance measuring apparatus may have components and functions that are not illustrated or described. The following description does not exclude components and functions that are not illustrated or described.

1 FIG. 1 FIG. 1 FIG. 1 1 1 is a block diagram illustrating a schematic configuration of a light projecting apparatusaccording to a first embodiment. The light projecting apparatusofhas a function of emitting a plurality of optical signals, and can be built in, for example, a distance measuring apparatus as described later. Note that the light projecting apparatusofcan also be used for various purposes other than the distance measuring apparatus.

1 2 3 2 3 2 3 2 3 2 2 3 1 FIG. The light projecting apparatusofincludes a plurality of light projecting unitsand a plurality of first control units. Each of the plurality of light projecting unitscan switch an emission direction and an emission timing of an optical signal. Each of the plurality of first control unitsis provided in association with any one of the light projecting units. Each of the plurality of first control unitscontrols the emission direction and the emission timing of the optical signal emitted from the corresponding light projecting unit. More specifically, each of the plurality of first control unitssupplies a control signal to the corresponding light projecting unit. Each light projecting unitemits an optical signal of an emission direction and an emission timing according to a control signal from the corresponding first control unit.

2 2 The optical signal emitted from each light projecting unitis a so-called laser light pulse. The laser light is coherent light having a uniform wavelength and phase, and has a single wavelength of 900 nm, for example. Note that the wavelength of the optical signal emitted from each light projecting unitis freely selectable.

2 2 2 The light intensity of the optical signal emitted from each light projecting unitgenerally needs to be a value conforming to a laser (eye safe) safety standard. By emitting an optical signal whose light intensity, pulse time, repetition frequency of pulses, and the like conform to the laser safety standard from each light projecting unit, even if the optical signal enters human eyes, there is no risk of damaging the human eyes. However, in a special environment that does not need to conform to the eye safe safety standard, each light projecting unitmay increase power, time, and the like of a laser pulse to extend a range of a distance measurement distance of a light detection and ranging (LiDAR) device.

2 2 2 2 As described above, in the present embodiment, the light intensity of the optical signal emitted from each light projecting unitis set to a value conforming to the laser safety standard. The higher the light intensity of the optical signal, the farther the optical signal can reach, but it is not preferable from the viewpoint of eye safe. Therefore, in the present embodiment, it is considered that an optical signal having light intensity conforming to the laser safety standard is emitted from each light projecting unit. Although the laser light has high rectilinearity, the beam size increases and the light intensity per unit area decreases as the optical path length increases. In the present embodiment, the beam of the plurality of optical signals emitted from the plurality of light projecting unitsat least partially overlap each other at a distant place. The light intensity increases in the region where the beam of the plurality of optical signals overlap each other. As described above, even if the light intensity of the optical signal emitted from each light projecting unitis not so high, the beam of the plurality of optical signals overlap each other at a distant place, so that the light intensity can be maintained high and the optical signal can reach a distant place.

2 FIG. 2 FIG. 2 2 2 2 2 2 is a perspective view of the plurality of light projecting units. As illustrated in the drawing, a plurality of the light projecting unitsare arranged in each of a horizontal direction X and a vertical direction Y.illustrates an example in which three light projecting unitsare provided in the horizontal direction X and four light projecting unitsare provided in the vertical direction Y, but the number of light projecting unitsis not limited. In addition, the plurality of light projecting unitsmay be arranged in a one-dimensional direction (the horizontal direction X or the vertical direction Y).

3 FIG. 3 FIG. 2 2 4 5 6 is a block diagram illustrating an example of an internal configuration of each light projecting unit. As illustrated in, each light projecting unitincludes a light source, an optical system, and a scanning unit.

4 4 4 4 4 4 3 The light sourceis the laser light sourcethat emits laser light as described above. The laser light sourceis, for example, a semiconductor laser. Alternatively, the laser light sourcemay be other than a semiconductor laser such as a HeNe laser. A pulsed optical signal is emitted from the light source. The light sourcecan switch an emission timing of an optical signal based on a control signal from the corresponding first control unit.

5 4 5 The optical systemshapes the optical signal emitted from the light source. Here, shaping means adjusting a beam shape and a traveling direction of an optical signal, a spread angle of a beam, and the like. An example of the optical systemis a collimator lens. The collimator lens can collimate the incident diffused optical signal.

6 5 6 3 6 3 The scanning unitscans the optical signal shaped by the optical systemwithin a predetermined light emission range. The scanning unitcan control the light emission range based on a control signal from the corresponding first control unit. The light emission range is a range of any size spreading in a two-dimensional direction or a one-dimensional direction. Furthermore, the scanning unitcan adjust the scanning speed when scanning the optical signal within the light emission range based on the control signal from the corresponding first control unit.

6 3 2 More specifically, the scanning unitincludes, for example, a micro-electro-mechanical systems (MEMS) mirror. The angle of the MEMS mirror can be electrically variable. When the angle of the MEMS mirror is changed, the reflection direction of the optical signal radiated to the MEMS mirror can be changed. Therefore, by changing the angle of the MEMS mirror based on the control signal from the corresponding first control unit, the emission direction of the optical signal emitted from each light projecting unitcan be changed little by little, and the optical signal can be scanned within a predetermined light emission range.

Some MEMS mirrors rotate about one axis, and some rotate about two axes. By using the MEMS mirror rotating about two axes and changing the angle of the MEMS mirror little by little in two axis directions, the optical signal can be scanned within the light emission range spreading in two-dimensional directions.

2 3 2 2 2 2 In this manner, each light projecting unitcan individually adjust the emission direction and the emission timing of the optical signal based on the control signal from the corresponding first control unit. Therefore, the plurality of optical signals emitted from the plurality of light projecting unitscan be emitted in substantially the same direction, and the optical signal can be emitted in any direction for each light projecting unit. In addition, all the light projecting unitscan emit a plurality of optical signals at substantially the same timing, or each light projecting unitcan emit an optical signal at any timing.

3 7 1 7 7 3 2 1 7 2 7 2 2 7 2 4 FIG. 1 FIG. 4 FIG. a a The plurality of first control unitsmay be controlled by the second control unit.is a block diagram of the light projecting apparatusin which the second control unitis added to the configuration of. The second control unitsupplies an angle command signal related to the emission direction of the optical signal to each of the plurality of first control units. The angle command signal is a signal that instructs the emission direction of the optical signal emitted from each of the plurality of first light projecting units. That is, in the light projecting apparatusof, the second control unitcontrols the emission direction of the optical signal emitted from each light projecting unit. By providing the second control unit, it is possible to collectively control in which direction the optical signal is emitted from the plurality of light projecting units, and it is easy to control the plurality of light projecting units. In addition, the second control unitmay control not only the emission direction of the optical signal emitted from each light projecting unitbut also the emission timing.

5 FIG. 5 FIG. 7 7 8 9 10 11 is a block diagram illustrating an example of an internal configuration of the second control unit. The second control unitofincludes a reference command generation unit, an angle correction table, a plurality of adders, and an update control unit.

8 2 8 8 10 The reference command generation unitgenerates a reference command signal commonly provided to all the light projecting units. The reference command signal is not necessarily one type. The reference command generation unitmay generate any of a plurality of types of reference command signals. The reference command signal generated by the reference command generation unitis input to the plurality of adders.

9 2 8 9 2 2 2 2 5 FIG. The angle correction tablestores an angle correction signal for correcting the reference command signal for each of the plurality of light projecting units. When the reference command generation unitgenerates one of the plurality of types of reference command signals, the angle correction tablestores the angle correction signal corresponding to each of the plurality of light projecting unitsfor each reference command signal. The angle correction signal includes an offset of an angle intended for each light projecting unitand an angle error of each light projecting unitdue to installation, manufacturing, and the like. For the data creation of the angle error, a laser may be emitted from each light projecting unitin advance, and the angle may be measured by a light receiving device, a photosensitive paper, or the like (not illustrated in).

9 7 9 9 2 As described above, the angle correction tablemay store a plurality of sets of correspondences between the reference command signals and the plurality of angle correction signals, and the plurality of angle correction signals may be different for each set. In this case, the second control unitselects one set from the plurality of sets stored in the angle correction table, reads the corresponding angle correction signal from the angle correction tablefor each of the plurality of light projecting unitsbased on the correspondence relationship of the selected set, and loads the reference command signal, thereby generating the angle command signal.

8 9 9 2 2 9 2 2 6 FIG.A 6 FIG.A Hereinafter, two specific examples of the plurality of types of reference command signals generated by the reference command generation unitand the angle correction tablewill be described.is a diagram showing a first specific example of the plurality of types of reference command signals. As shown in, the reference command signal in the first specific example is a signal instructing continuous or stepwise change of the emission direction according to time for each cycle. The reference command signal is an analog value or a digital value, and may be a voltage signal or a current signal. The angle correction tablestores, for example, an angle correction signal for making the emission direction parallel for each of the plurality of light projecting units. For example, in a case where the emission direction of one of the two adjacent light projecting unitsis shifted by plus 1 degree from the other light projecting unit in the default state, the angle correction tablesets the angle correction signal of the emission direction of one of the two light projecting unitsto 0 degrees and sets the angle correction signal of the emission direction of the other to −1 degrees. As a result, the emission directions of the optical signals emitted from the two light projecting unitscan be made parallel.

6 FIG.B 6 FIG.B 6 FIG.B is a diagram showing a second specific example of the plurality of types of reference command signals. The reference command signal in the second specific example is emitted a plurality of times at predetermined time intervals, and becomes a pulse train signal as shown in. The emission direction of each reference command signal is changed by an angle corresponding to the number of times of emission of the optical signal. For example, when the emission direction of the optical signal is changed by m degrees every time the reference command signal is emitted, the emission direction of the n-th reference command signal is changed by m×n degrees as compared with the first reference command signal. As shown in, the emission direction is periodically changed in a range of 0 to 360 degrees.

9 9 2 Similarly to the angle correction tablein the first specific example, the angle correction tablein the second specific example stores, for example, the angle correction signals such that the emission directions of the optical signals emitted from the plurality of light projecting unitsare parallel.

9 Note that the plurality of types of reference command signals and the angle correction signals stored in the angle correction tableare not necessarily limited to the first specific example and the second specific example described above.

10 3 10 9 3 The plurality of addersare provided in association with the plurality of first control units. Each of the plurality of addersadds the reference command signal and the corresponding angle correction signal read from the angle correction tableto generate a corresponding angle command signal for the first control unit.

9 11 7 9 9 11 2 1 11 8 a The angle correction signal stored in the angle correction tablemay be updated as necessary. For example, the update control unitin the second control unitupdates the angle correction signal stored in the angle correction table. By updating the angle correction signal stored in the angle correction tableby the update control unit, the emission directions of the optical signals emitted from the plurality of light projecting unitscan be switched as necessary, and the reconfigurable light projecting apparatuscan be realized. Note that the update control unitand the reference command generation unitmay be integrated.

7 3 7 3 5 FIG. The second control unitis not necessarily configured as illustrated in. For example, without providing the reference command signal, the angle command signals for the plurality of first control unitsmay be directly generated by the second control unitand supplied to the corresponding first control units.

1 1 2 2 2 a 1 5 FIGS.to In the light projecting apparatusesandof, the configuration in which the emission direction of the optical signal emitted from each of the plurality of light projecting unitscan be individually controlled has been described, but the plurality of light projecting unitsmay be integrated to collectively scan the plurality of optical signals emitted from the plurality of light projecting unitsin the one-dimensional direction or the two-dimensional direction.

7 FIG. 4 FIG. 8 FIG. 7 FIG. 8 FIG. 1 12 1 12 2 12 1 b b b is a block diagram illustrating a schematic configuration of a light projecting apparatusin which a scanning control unitis added to the configuration of, andis a perspective view of the light projecting apparatusof. The scanning control unitperiodically scans the optical signals emitted from the plurality of light projecting unitsintegrally in a one-dimensional direction or a two-dimensional direction. For example, as illustrated in, the scanning control unitmay cause the light projecting apparatusto periodically scan at least one of the horizontal direction X and the vertical direction Y for each housing thereof.

1 2 3 12 b 7 FIG. According to the light projecting apparatusof, the emission directions of the plurality of optical signals emitted from the plurality of light projecting unitscan be individually controlled by the corresponding first control units, and the emission directions of the plurality of optical signals can be integrally controlled by the scanning control unit.

1 1 1 2 3 2 3 2 2 a b As described above, the light projecting apparatuses,, andaccording to the first embodiment include the plurality of light projecting unitsand the plurality of first control units, and the emission direction and the emission timing of the optical signal emitted from each of the plurality of light projecting unitsare controlled by the corresponding first control unit. As a result, the emission direction and the emission timing of the optical signal emitted from each of the plurality of light projecting unitscan be individually and arbitrarily adjusted, and the plurality of optical signals emitted from the plurality of light projecting unitscan be used for various applications.

7 3 7 3 1 1 1 2 a b In addition, since the second control unitthat controls the plurality of first control unitsis provided and the angle command signals are supplied from the second control unitto the plurality of first control units, it is possible to realize the reconfigurable light projecting apparatuses,, andin which the emission directions and the emission timings of the optical signals from the plurality of light projecting unitsare changed by updating the angle command signals as necessary.

1 1 1 1 7 2 2 a b a b 4 7 FIGS.to Light projecting apparatusesandaccording to a second embodiment have a block configuration similar to that in. In the light projecting apparatusesandaccording to the second embodiment, the second control unitcontrols the plurality of light projecting unitsso that optical signals traveling substantially in parallel are emitted from the plurality of light projecting units.

9 FIG. 9 FIG. 4 FIG. 2 2 2 3 7 3 2 3 2 3 2 7 2 is a diagram schematically illustrating beam shapes of optical signals emitted from the plurality of light projecting units. As illustrated in, the plurality of optical signals emitted from the plurality of light projecting unitstravel in substantially parallel directions. The emission direction of the optical signal emitted from each of the plurality of light projecting unitsis controlled by the corresponding first control unit. As illustrated in, an angle command signal is supplied from the second control unitto each of the plurality of first control unitscorresponding to the plurality of light projecting units. Each of the plurality of first control unitscontrols the emission direction of the optical signal emitted from the corresponding light projecting unitbased on the corresponding angle command signal. In the case of the present embodiment, the corresponding first control unitcontrols the emission direction of the optical signal emitted from the corresponding light projecting unitby the angle command signal from the second control unit, and the plurality of optical signals emitted from the plurality of light projecting unitsare made substantially parallel.

2 2 10 1013 FIGS.A and 10 FIG.A 10 FIG.B The beam width of the optical signal emitted from each light projecting unitincreases as it goes farther, but the degree of spread of the beam width is different between the horizontal direction and the vertical direction.are diagrams schematically illustrating the beam width of the optical signal emitted from each light projecting unit,illustrates a change in the beam width in the horizontal direction, andillustrates a change in the beam width in the vertical direction.

2 10 FIG.A 10 FIG.B In the optical signal emitted from each light projecting unit, the beam width in the horizontal direction hardly changes even when the distance changes as illustrated in, whereas the beam width in the vertical direction greatly changes according to the distance as illustrated in. More specifically, the beam width in the vertical direction increases as the distance increases.

2 2 1 1 a b By arranging the plurality of light projecting unitsin the vertical direction, a region in which the optical signals emitted from the plurality of light projecting unitsoverlap each other in the vertical direction is generated at a place distant from the light projecting apparatusesand. In this region, the light intensity is higher than that of a single optical signal.

2 2 2 2 10 FIG.B As described above, in the second embodiment, the plurality of optical signals are emitted from the plurality of light projecting unitsin the substantially parallel direction, and the plurality of optical signals emitted from the plurality of light projecting unitspartially overlap each other in the vertical direction, so that the light intensity at a distant place can be increased. As illustrated in, when the interval between the plurality of light projecting unitsarranged in the vertical direction changes, the range in which the plurality of optical signals overlap each other in the vertical direction at a distant place changes. If each laser beam does not spread so much and overlaps at a short distance where the laser intensity is strong, the overlapping portion may not be eye safe compliant. Therefore, it is desirable to adjust the interval between the plurality of light projecting unitsarranged in the vertical direction so that the overlapping range can conform to the eye safe standard.

1 1 2 1 1 1 1 2 a b a b a b In addition, in the light projecting apparatusesandaccording to the second embodiment, the plurality of light projecting unitsmay emit optical signals at substantially the same emission timing. For example, in the distance measuring apparatus which is an application example of the light projecting apparatusesandaccording to the present embodiment, the optical signal is repeatedly emitted at predetermined time intervals, the reflected optical signal from the object is repeatedly received, and the distance to the object is measured based on the light reception result. As described above, in a case where the light projecting apparatusesandaccording to the present embodiment are used in the distance measuring apparatus, the operation of emitting the optical signals from the plurality of light projecting unitsat substantially the same timing is repeatedly performed at predetermined time intervals, and the reflected optical signal from the object is repeatedly received to measure the distance to the object.

1 1 2 2 2 a b Light projecting apparatusesandaccording to a third embodiment classify the plurality of light projecting unitsinto a plurality of light projecting groups. In the second embodiment, the example in which the plurality of light projecting unitsemit the plurality of optical signals in substantially the same emission direction has been described, but in the third embodiment, the plurality of light projecting unitsare classified into two or more light projecting groups, and the emission direction of the optical signal is individually controlled for each light projecting group.

2 2 2 More specifically, in the third embodiment, N (N is an integer of 2 or more) light projecting unitsare classified into M (2<M N) light projecting groups, and the light projecting unitsbelonging to the same light projecting group emit optical signals in the same emission direction. In addition, the light emission ranges of the light projecting unitsbelonging to different light projecting groups do not overlap each other or only partially overlap each other.

1 1 2 2 6 2 2 a b As a result, the light emission ranges of the light projecting apparatusesandincluding the plurality of light projecting unitscan be wider than the light emission range of the single light projecting unit. For example, in the case where the MEMS mirror is used in the scanning unitof the light projecting unit, the light emission range of the light projecting unitis narrowed because the drive range of the MEMS mirror is narrowed. Therefore, by providing a plurality of MEMS mirrors, the light emission range as a whole can be expanded.

11 FIG. 11 FIG. 1 1 2 2 1 2 2 2 3 a b is a diagram schematically illustrating characteristic portions of the light projecting apparatusesandaccording to the third embodiment.illustrates an example in which a plurality of (for example, four) light projecting unitsare classified into three light projecting groups (hereinafter, first to third light projecting groups)-,-, and-, and the emission direction of the optical signal is individually controlled for each light projecting group.

2 2 1 1 2 2 2 2 2 2 3 3 1 2 3 2 2 1 2 2 2 2 2 3 11 FIG. The light projecting unitbelonging to the first light projecting group-scans the optical signal in a first light emission range OR. The light projecting unitbelonging to the second light projecting group-scans the optical signal in a second light emission range OR. The light projecting unitbelonging to the third light projecting group-scans the optical signal in a third light emission range OR.illustrates an example in which the first light emission range OR, the second light emission range OR, and the third light emission range ORdo not overlap each other, but may partially overlap each other. That is, the emission direction of the optical signal emitted from the light projecting unitbelonging to the first light projecting group-, the emission direction of the optical signal emitted from the light projecting unitbelonging to the second light projecting group-, and the emission direction of the optical signal emitted from the light projecting unitbelonging to the third light projecting group-may be completely different from each other, or may partially overlap each other.

11 FIG. 2 1 2 3 1 1 a b As can be seen from, since the light emission ranges of the first to third light projecting groups-to-are at least partially different from each other, the light emission range of the entire light projecting apparatusesandcan be expanded more than the light emission range of one light projecting group.

2 3 2 The manner of classifying the plurality of light projecting unitsinto the plurality of light projecting groups may be determined in advance. In this case, the first control unitcorresponding to each light projecting unitmay grasp the emission direction and the emission timing of the optical signal.

2 7 2 7 3 2 7 3 Alternatively, what kind of light projecting group the plurality of light projecting unitsare classified into may be arbitrarily adjusted. In this case, the second control unitperforms control to classify the plurality of light projecting unitsinto a plurality of light projecting groups. The second control unittransmits, to the plurality of first control units, information regarding to which light projecting group the corresponding light projecting unitbelongs. The information transmitted from the second control unitto the plurality of first control unitsalso includes information indicating the light emission range of each light projecting group.

7 2 1 1 7 2 2 1 2 3 a b 11 FIG. By allowing the second control unitto change the light projecting group into which the plurality of light projecting unitsare classified as necessary, it is possible to realize the reconfigurable light projecting apparatusesand. In addition, the second control unitmay control the timing at which the plurality of light projecting groups emit the optical signal. For example, in the case of, the light projecting unitsbelonging to the first to third light projecting groups-to-may emit optical signals at substantially the same timing, or may emit optical signals at different timings.

2 2 1 1 2 1 1 a b a b. As described above, in the third embodiment, since the plurality of light projecting unitsare classified into the plurality of light projecting groups and the light emission direction is controlled for each light projecting group, the light emission range can be expanded as compared with the case where the light emission ranges of the plurality of light projecting unitsare aligned. Therefore, in a case where the light projecting apparatusesandaccording to the present embodiment are applied to the distance measuring apparatus, it is possible to measure a distance to an object present in a wider range, and practicality is enhanced. In addition, by changing which light projecting unitis classified into which light projecting group as necessary, it is possible to realize the reconfigurable light projecting apparatusesand

1 1 1 a b As described above, the light projecting apparatuses,, andaccording to the first to third embodiments can be applied to the distance measuring apparatus.

12 FIG. 12 FIG. 21 1 1 1 21 1 1 1 22 23 a b a b is a block diagram illustrating a schematic configuration of a distance measuring apparatusincorporating the light projecting apparatuses,, andaccording to any one of the first to third embodiments. The distance measuring apparatusofincludes the light projecting apparatuses,, andaccording to any one of the first to third embodiments, a light receiving device, and a distance measurement unit.

22 1 1 1 22 a b The light receiving devicereceives a reflected optical signal obtained by reflecting a plurality of optical signals emitted from the light projecting apparatuses,, andby an object. The light receiving devicemay include a light receiving module in which a plurality of light receiving elements are two-dimensionally arranged. The light receiving element may be a single photo avalanche diode (SPAD). Since the SPAD can detect one photon, it is possible to detect a weak reflected optical signal from a distant object.

21 1 1 1 22 a b The distance measuring apparatusmeasures the distance by, for example, a direct time of flight (dToF) method. In the dToF method, the distance to the object is measured based on the time difference between the timing at which the light projecting apparatuses,, andemit the optical signal and the timing at which the light receiving devicereceives the reflected optical signal.

7 21 3 2 3 2 12 FIG. The second control unitin the distance measuring apparatusofmay supply the angle command signals to the plurality of first control unitsso that the plurality of light projecting unitsemit the optical signal in substantially the same emission direction, or may supply the angle command signal to the corresponding first control unitfor each light projecting group obtained by classifying the plurality of light projecting unitsinto a plurality of light projecting groups.

2 21 22 23 2 As described above, each light projecting unitin the distance measuring apparatusrepeatedly emits the optical signal while scanning the optical signal in the two-dimensional direction within the predetermined light emission range, the light receiving devicecontinuously receives the reflected optical signal, and the distance measurement unitmeasures the distance to the object based on the light reception result. The cycles in which the light projecting unitsscan the optical signal within the light emission range are not necessarily the same.

2 2 2 Assuming that each light projecting unitemits the optical signal at a predetermined time interval (for example, a time interval determined by the eye safe reference), as the time during which each light projecting unitscans the optical signal in the light emission range is longer, the number of optical signals emitted from each light projecting unitincreases while the light emission range is scanned, and the presence or absence of an object in the light emission range and the shape of the object can be detected more accurately.

13 FIG. 12 FIG. 21 24 25 a is a block diagram of a distance measuring apparatusin which an object detecting unitand a scanning speed adjusting unitare added to the configuration of.

24 2 25 25 2 The object detecting unitdetects an object present in the light emission range while the plurality of light projecting unitsscan the optical signals in the light emission range. The scanning speed adjusting unitadjusts the length of the cycle in which the optical signal scans the light emission range. More specifically, the scanning speed adjusting unitmakes the scanning speed when the optical signal is scanned within the range where the object detected by the object detecting unit is present slower than the scanning speed when the optical signal is scanned outside the range. It is assumed that each light projecting unitemits an optical signal at a constant time interval.

21 25 24 22 1 1 1 a a b 13 FIG. In the distance measuring apparatusof, the scanning speed adjusting unitsets the length of the cycle in which the optical signal scans the light emission range to a first scanning cycle, and then starts a distance measuring operation. The object detecting unitdetects whether or not the light receiving devicehas received the reflected optical signal from the object while the light projecting apparatuses,, andare scanning the light emission range with the first scanning cycle.

22 24 24 When the signal level of the light reception signal of the light receiving deviceis equal to or higher than a predetermined threshold level, the object detecting unitdetermines that the reflected optical signal has been received. The object detecting unitdetects all objects present in the entire light emission range.

25 For example, in a case where one object is detected in the light emission range, the scanning speed adjusting unitdecreases the scanning speed of the optical signal when scanning the vicinity of the detection position of the object in the light emission range. As a result, more optical signals can be emitted in the vicinity of the detection position of the object in the light emission range, and the depth shape of the object can be detected more accurately.

14 FIG. 14 FIG. 14 FIG. 26 26 26 26 illustrates an example in which one object (vehicle in the example of)is present in the lower right region in the light emission range. Each square in the light emission range inindicates the emission timing of the optical signal. In the vicinity of the detection position of the object, the size of the square is small, indicating that more optical signals are radiated to the vicinity of the detection position of the objectto more finely detect the depth shape of the object.

14 FIG. On the lower side of, a timing chart in a case where the light emission range is scanned twice is shown. Hereinafter, a scanning cycle at a first time is referred to as a first scanning cycle, and a scanning cycle at a second time is referred to as a second scanning cycle.

14 FIG. 14 FIG. 1 4 4 9 2 2 3 22 24 26 In the lower right timing diagram of, the horizontal axis represents time, and the vertical axis represents a scanning position within the light emission range. The vertical axis may be a scanning angle. In, time tto time tare the first scanning cycle, and time tto time tare the second scanning cycle. In the first scanning cycle, since each light projecting unitscans the optical signal at a constant scanning speed, the scanning position changes linearly with time. A period from time tto time tin the first scanning cycle is a period for scanning a region where the vehicle is present in the light emission range. Since the signal level of the light reception signal received by the light receiving deviceincreases in this period, the object detecting unitdetects the object.

26 25 2 26 26 In the second scanning cycle, the optical signal is initially scanned at the same scanning speed as in the first scanning cycle. When the scanning position of the optical signal is near the position of the object, the scanning speed adjusting unitdecreases the scanning speed of the optical signal. As described above, since each light projecting unitemits the optical signal at regular time intervals, when the scanning speed of the optical signal decreases, it is possible to emit more optical signals while scanning the vicinity of the position of the object. Therefore, the depth shape of the objectcan be detected more accurately.

14 FIG. 4 5 1 4 26 5 8 26 6 7 6 7 26 2 3 26 6 7 26 2 3 In, at time tto time t, the scanning position changes at the same inclination as that at time tto time tnear the position of the object, whereas, at time tto time t, the change in the scanning position per unit time becomes smaller. The objectis detected in a period from time tto time t. A period tto tduring which the objectis detected in the second scanning cycle is longer than a period tto tduring which the objectis detected in the first scanning cycle. Therefore, in the period from time tto time t, the objectcan be irradiated with more optical signals than during the period from time tto time t.

15 FIG. 15 FIG. 15 FIG. 26 2 26 26 2 2 is a diagram illustrating an example in which a plurality of (two in the example of) objectsare detected in the light emission range. In this case, the plurality of light projecting unitsare classified into a plurality of light projecting groups according to the number of detected objects. In the case of, since two objectsare detected in the light emission range, the plurality of light projecting unitsare classified into two light projecting groups. The number of the light projecting unitsbelonging to each light projecting group is freely selectable.

15 FIG. 1 6 6 15 24 26 24 26 22 In, time tto time tare the first scanning cycle, and time tto time tare the second scanning cycle. In the first scanning cycle, the entire region in the light emission range is scanned at a constant scanning speed. While the inside of the light emission range is scanned in the first scanning cycle, the object detecting unitdetects two objectsin the light emission range. As described above, the object detecting unitdetects the objectwhen the signal level of the light reception signal of the light receiving deviceexceeds the predetermined threshold.

24 26 2 3 4 5 The object detecting unitdetects two objectsat time tto time tand time tto time tin the first scanning cycle.

3 2 2 1 2 2 26 26 24 2 2 1 26 26 2 2 2 26 26 2 1 6 7 10 15 7 10 26 26 8 9 2 2 6 11 14 15 11 14 26 26 12 13 a b a a b b 15 FIG. The first control unitclassifies the plurality of light projecting unitsinto, for example, two light projecting groups (the first light projecting group-and the second light projecting group-) since two objects (a first object and a second object)andare detected by the object detecting unit, and decreases the scanning speed when the two light projecting unitsbelonging to the first light projecting group-scan the vicinity of the position of the first objectto more accurately detect the depth shape of the first object. In addition, the scanning speed is decreased when the two light projecting unitsbelonging to the second light projecting group-scan the vicinity of the position of the second objectto more accurately detect the depth shape of the second object. In the example of, the first light projecting group-scans the optical signal in the periods from time tto time tand from time tto time tin the second scanning cycle in the same cycle as the first scanning cycle. In the period from time tto time t, the scanning speed of the optical signal is reduced because the position is near the position of the object. The objectis detected in a period from time tto time t. On the other hand, the second light projecting group-scans the optical signal in the periods from time tto time tand from time tto time tin the second scanning cycle in the same cycle as the first scanning cycle. In the period from time tto time t, the scanning speed of the optical signal is reduced because the position is near the position of the object. The objectis detected in a period from time tto time t.

15 FIG. 26 26 26 As illustrated in, if the depth shape of the objectis detected by slowing the scanning speed by a separate light projecting group for each objectdetected in the light emission range, the depth shape of each objectcan be accurately detected without making the second scanning cycle longer than the first scanning cycle.

1 1 1 21 21 26 a b a As described above, in the fourth embodiment, since the light projecting apparatuses,, andaccording to the first to third embodiments are applied to the distance measuring apparatusesand, an objectin a wide range can be accurately detected.

21 26 26 26 a 13 FIG. Furthermore, in the distance measuring apparatusof, when the objectis detected in the light emission range, the scanning speed is reduced when the vicinity of the position of the detected objectis scanned with an optical signal. As a result, the depth shape of the objectcan be detected more accurately.

26 2 26 26 26 Furthermore, in a case where a plurality of objectsare detected in the light emission range, the plurality of light projecting unitsare classified into a plurality of light projecting groups in accordance with the number of detected objects, and the corresponding objectscan be detected at a slow scanning speed in each light projecting group, so that the depth shapes of the plurality of objectsin the light emission range can be accurately detected.

While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the disclosures. Indeed, the novel methods and systems described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the methods and systems described herein may be made without departing from the spirit of the disclosures. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the disclosures.